Wellbore operations employ pipe strings, sometimes called drill, production or work strings, each used for drilling and/or servicing. The pipe string can comprise a bottom hole assembly such as, when drilling, a drill bit attached to sections of drill pipe. As the well is drilled or serviced, additional sections of drill pipe are added to the pipe string to extend its length until the bottom hole assembly is deep enough to reach a depth of interest. Sections of pipe are joined together using threaded connections on the pipe, often referred to as “pin” and “box” connections, where the pin of one section of pipe is threaded into the box of an adjoining section of pipe. When the pipe string is removed from the wellbore, the sections of pipe can be removed from the pipe string by unthreading the connections and setting aside a pipe section.
While servicing or drilling wells, a BOP (blowout preventer) is installed on the wellhead. The purpose of the BOP is to close off the well in the event of an emergency and to seal the well while normal servicing or drilling operations are being conducted. To prevent the drill string from falling into the well, a device called “slips” are employed. The slips are a mechanical device with a set of jaws that allow the drill string to be moved up out of the well, with the slips acting to arrest automatically the drill string if it starts falling into the well. The slips can be unlocked to allow controlled movement of the drill string into the well, when desired.
Currently, the slips are positioned atop the BOP and are free to slide around relative to the BOP. This allows the driller to move the drill string with respect to the well casing and slips will slide to follow the string. It is desirable to move the drill string with respect to the well casing because often it is a requirement for multiple strings to be positioned in the well side by side and, so, the string to be controlled is off center.
However, the slips, being free to slide, are difficult to use in a slant rig. The slant orientation may tend to pull the slips to the low side. In addition, since the movement of the slips cannot currently be controlled, it is difficult to move and hold the slips in a position suitable to locate the drill string, as desired by the driller. Because of this, dangerous, time consuming and inefficient methods may be employed to move the slips and the drill string to the desired location and to counteract gravitational issues when operating in slant.